[Pitch] Optional.orThrow

[xwu (Xiaodi Wu)]

See also previous threads on this topic:

Throw on nil

I find myself wanting to define an operation that converts failable initializers to throwing ones. When I have a throwing initializer contains multiple failing initializers, I think it improves the clarity and readability of the code. (see below) UPDATE: Leaving the original implementation but I am not opposed to changing the spelling or making this an operator or whatever. Lots of great ideas and info below. extension Optional { func orThrow(_ error: @autoclosure () -> Error) throws -> W…

Combining ? with throwing when there's no reasonable default

If we want to say, "use this or if it's nil, that default", we can write: let a = maybeA ?? A() However, saying "use this or if it's nil, throw" is more verbose (if descriptive): guard let a = maybeA else { throw SomeError() } One might imagine writing let a = maybeA ?? throw SomeError() but this doesn't work: throw X is a statement, not an expression, so it doesn't parse. As @Nevin notes, we can make the right-hand side an explicit closure evaluation: let a = try maybeA() ?? { throw Som…

In particular, re @ellie20's comment, see:

Combining ? with throwing when there's no reasonable default

I agree. Several other things were different back in Swift 1 days while we were discussing this - e.g. we didn't have Never at the time. I'm +1 on moving throw to being an expression.